this weekend in washington, meantime, president obama giving the odds of achieving a long-term agreement with iran 50/50 at best. >>> meantime, the pentagon under fire tonight for its decision to buy combat helicopters made in russia. lawmakers on both sides, asking, why not made in america? here tonight, abc's aditi roy. >> reporter: tonight, new questions arise as to why the pentagon chose to spend more than $1 billion on dozens of russian mi-17 helicopters, to support afghan troops, bypassing u.s. manufacturers. the defense department signed the deal more than two years ago and pentagon officials defended the move, citing a 2010 top secret study, which they said recommended the russian helicopter as the top choice. but the associated press has obtained excerpts of the study, which said the u.s. manufactured chinook helicopter was the, quote, most cost effective single platform type fleet for the afghan air force over a 20-year period. the russian deal sparking outrage in congress, as lawmakers pressed officials during defense department budget hearings in april. >> with all the tens o